International 15-year study shows most dominant HIV subtype is also 'wimpiest'

An international study 15 years in the making has shown that it's 'survival of the wimpiest' among subtypes and strains when it comes to understanding the spread of HIV/AIDS around the world, a virus that has killed an estimated 35 million people since the 1970s.

Dating back to the early 2000s, Eric Arts, Chair of the Department of Microbiology & Immunology at Western University's Schulich School of Medicine & Dentistry, co-led a research team that monitored approximately 300 women in Uganda and Zimbabwe newly infected with HIV and examined their physical and mental health, as well as their social and behavioural patterns, for close to a decade in some cases.

Arts and his collaborators discovered that a group of infected women progressed very slowly to AIDS and discovered that nearly all were infected with a specific HIV-1 strain, called subtype C. This HIV-1 strain replicates very poorly and very slowly in patients making it the "wimpiest" subtype of the deadly virus despite also being the most dominant form of HIV in the world, predominantly found in Southern Africa, Eastern Africa, India, Nepal, and parts of Brazil and China.

These findings, published today by the journal EBioMedicine, appear counterintuitive to Darwinian evolutionary theory, which promotes the fittest not the wimpiest as the standard for reproductive success.

"Understanding that HIV subtype C is 'wimpy' is a difficult proposition because seeing it replicate poorly in tissue culture flasks does not mean that it will establish a slower infection in an infected individual. But that's exactly what happens," explains Arts, the Tier 1 Canada Research Chair in HIV Pathogenesis and Viral Control. "Based on our study, it is very clear that patients infected with HIV subtype C progress slower to full-blown AIDS."

Arts led the study with collaborators from Western, Case Western Reserve University, the Joint Clinical Research Centre in Kampala, Uganda, Makerere University in Kampala, Uganda, the University of Zimbabwe, and Family Health International 360.

Colin Venner, a graduate student in the Arts Lab and lead author of the study, says that the growth of HIV subtype C from the early 1990s to where it is now has been very pronounced.

"A lot of people see the dramatic growth of HIV subtype C and think it would be the strongest virus and that it's beating all of the other subtypes but really, viruses are commonly transmitted, especially in southern and eastern Africa, in a period of asymptomatic disease," explains Venner. "These patients are maybe not aware that they're infected and that's when they're transmitting the most. The longer a patient is asymptomatic, the more likely they are to transmit to others is one of the thoughts that we're working on right now."

Arts believes knowing the virulence of the different HIV subtypes could have a major impact on how the virus is treated with drugs throughout the world.

"Unfortunately, we still don't have a vaccine that is effective in protecting against HIV but in treatment, if we know a patient progresses very slow to disease and the virus is having a minimal impact on the immune system then all of the devastating consequences of delaying treatment, as we saw in North America, may not be as pronounced in patients infected with HIV subtype C," offers Arts. "When we are looking at billions and billions of dollars a year to treat the global epidemic, we might have to look it as who needs treatment immediately and who can be delayed. That's very controversial but it's something that we have to consider for further study."

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